Nonstatic photographic film



Jan. 19 1926. 1,570,077

` Y E.. c. PrrMAN Jens/Yge'a Emu/sion.

Patented J an. 19, 1926.

UNITED s'lA'rEs P'A'rlazlxlf'il OFFICE.

EAELE c. PITMAN, or PAELIN, NEW JEEsEY, AssIeNon To E. 1. DU roNT DE NEMUns a COMPANY, or WILMINGTON, DELAWARE, A coEroEATIoN or DELAWARE. 1

y NONSIATIC PHlO-'IOGBAPHIC FILM.

Application led September 16, 1920, Serial No. 410,747.' Renewed Tune 22, 1925.

To all whom-t may concern: l

Be it known that I, EARLE C. PITMAN, a citizen of the United States,and a' resident of Parlin, in the county of Middlesex and State of New Jersey, have invented a certain new and usefulv Nonstatic Photographic Film, of Which th'e following is a specification. y

This invention relates to photographic films having provisions for the elimination of discharges of static electricity. With the ordinary film these discharges occur when the film isstripped from thecasting surface, when it is. run rapidly through a cinematographic camera and under various other cir-v cumstances. Such discharges cause markings on the sensitized emulsion by premature exposure thereof. It is an object of the invention to provide a film which, for practical purposes of manufacture and use, will be free from static electricity, and' itais also an object to improve generally upon films of the character indicated.l

For convenience and lbrevity of description I use the term film to denote the enthe term backing to denote a layer of a composite film bod which lies adjacent the other side of the filym body from the side intended to directly carry the emulsion; a-nd I use the term base to denote the portion of a composite film` body which is intended to carryI the backing at one side and the emulsion at the other and to forni or in- 'clude the principal strength-giving portion of the film. On occasion, as will appear from the context, I use the term base (or pellicle base) to also indicate the substance,

as cellulose acetate, which is the primary substanceused to form a pellicle.

In the accompanying drawing I have,

without restricting my. invention thereto,- shown a film embodying my invention, the l viewbeing a conventional, exaggeratedh cellulose acetate decreases in hygroscopicity cross-sectional showing.

"fAccording to my invention, I 4use in the -fllm body asubstance, or'substances, which Willmakethe body, either as a whole, orat -i'tspbacking-,where one is used, more electricallyjgconductive than is the ordinary film. In this; way,. j;-I provide that such static charges as tend to be generated shall leak away, be neutralized, or beevenly distrlbuted, before they can accumulate in such a way, or to suchamount, as `to-be liable to4 harmful discharge. Y

Thus,.I- may incorporate in the body a hygroscopic substance such as glycerine,

either alone or in combination with an eleccorporated, and to b'e such as -not to cause precipitation of the pellicle base, as cellulose acetate, used for the pellicle. The hygroscopic substance increases the, conductivity by increasing the moisture content; the electrolyte increases the conductivity of any moisture resent. The electrolyte is, of, course, va uable, whether or nota hygroscopic substance vis used also, as some moisture is .present in any case.

The various substancesl may rated in a body having any desired pellicle base and without a backing, or may be incorporated in av backing and such backing appliedto any desired base. The backing ma .be one which primarily functions merely by virtue of the substances and, so, may not contain a pellicle base, e. cellulose acetate; or it may contain a pellicle base of' any suitable character and either having be incor o- I substantially the same conductivity as the Y fpellicle base used in making .the base of the film, or having a conductivity somewhat greater than that of the pellicle-base used in makin the base of I,the film and enabling the pe licle base of the backing to itself serve in giving the backing a superior conductivity'.

As to the use for the backing of a pellicle i base whichis itself of superior conductivity, I may appl abackiiig layer of carbohydrate ester of re atively low esterification, e; g., cellulose acetatecontaining 55% combined acetic acid or less, that is, of not over 55% combined acetic acid. I have found that and in conductivity as the combined acetic acid content increases, though it increases in strength,.so that cellulose acetate containing not over-55% coiibinedl acetic. acid is more hygroscopic and more conductive than cellulose acetate containing more than 55% combined acetic acid; yet experience has shown that, if proper strength is to be secured in a cellulose acetate film, then a film primarily of cellulose acetate of more than 55% combined acetic acidlis a practical necessity, despite the fact that, used alone, it is liable to static discharges due to its non-conductivity. So, in carrying out my invention, I apply a backing ofcellulose acetate of 55% or less combined acetic acid, preferably about 54%, to a base of cellulose acetate of more than 55% combined acetic acid, preferably about 59%. In this Way I produce a cellulose acetate film which has the strength demanded by the trade and lvet is conductive and substantially non-static. As will he understood, a film lof the character just indicated may, if desired, contain no added hygroscopic or electrolytic substances and yet present the advantage of conductivity to a marked degree. In such cases any suitable formulas for the base and the backing solution may be used; conveniently the below-given formulas 3, and

l or 3, each with the glycerine omitted, Gly

may be usedV for the base, and the backing, respectively.

While the above mentioned cellulose acetate backing is highly advantageous of 1tself, either when applied to any suitable film base or, particularly, when applied to the mentioned cellulose acetate film base, I have found, as previously indicated, that the incorporation, in such a backing; of conductivity-increasing substances, as a hygroscopic substance, alone or in combination with an electrolytic substance, gives a particularly satisfactory4 fihn.

The mechanical operations -of making films in accordance with my invention Will be evident to those skilled in the art, the casting of films, and similar operations, as such, being, of course, Well known in the? art. The backing solution may be applied, and the solvents evaporated to give the backing, in any convenient manner. Below I give formulas illustrative of fihns embodying my invention, it being understood that I do not restrict the invention to the examples given. In the formulas, figures refer to parts by weight. il (l) For a backing containing a hygroscopic substance, glycerine, the following formula may be used In makin up, to the combined solvents add (a) the g ycerlne and (b) the cellulose acetate 1n order.

(2) For a backing containing a hygroscopic substance, glycerine, and an electrolyte, ammonium acetate, the formula, as to ingredients, ranges, and preferred amounts,

1 part, of amdesired thickness serving the ends sought,

I have found a relatively thin backing` desirable. A' film base for them may be 3, glyccrine omitted. (3) For a film body not having a back ing but yet containing a hygroscopic substance, glycerine, I recommend the following formula.v

Approximate Prerange. ferred.

Cellulose acetate (dry) 25 to 30 cerine 0.25 to 15 1 Acetone 100 to 140 120 Wood alcohol 60 to 100` Triacetin 3 to 15 6 In preparing, to the combined solvents add (a) the gl cerine and (b) the cellulose acetate in or er.

(4) For a similar fihn` body containing a hygroscopic substance, glycerine, and an.y

electrolyte, ammonium acetate, the formula, as to ingredients, ranges, and preferred amounts,may be the same as 3 except that it should include, in addition, approximately 0.25 to 10 parts, preferably 1 part, of ammonium acetate. When making up, to the combined solvents add (a) the ammonium acetate, (b) the glycerine, and (c) the cellulose acetate, in order.

I would call attention to the fact that the vabove compositions are v`substantially neutral, vas is evident from consideration of the ingredients thereof, they having neither a pronounced alkaline or acid reaction. In consequence, the composition Will have substantially no harmful effect upon metallic casting surfaces, a feature of particular importance in connection with the making of the film body; and in further consequence, the film body itself, and the backing itself, although containing, of course, residual solvent to assist in flexibility, will have no desensitizing effect on the emulsion. vThis is of importance not only with respect to a film body, the emulsion being spread upon that, but also with respect to a backing since when a film is rolled upon 'itself (no shielding paper being used) as in motion picture films, the backing of one coil/ comes into direct contact with they emulsion of the next coil.

In all 'the above formulas the` cellulose acetate may have or less combined acetic acid, or may have more than 55% combined acetic acid, but, as explained above, 4it is desirable that cellulose acetate having' 55% or less combined acetic acid, that is not over 55% combined acetic acid, be used for the backings,' and that such backings be applied to a ,base of cellulose acetate having more than 55% combined acetic acid. In the cases`of u'nbacked filmsit is desirable to use cellulose acetate having more than combined acetic acid.

To provide backings which are soluble in water and can be totally 're-moved, say in development, (after which there is no longer any (langer from static marks), glycerine and ammonium acetate in the" preferred amounts and ranges given in formulas l and 2 may be dissolved in l100 to 400, preferably 200, parts of denatured alcohol. L

Although, for purposes of specific illustration, I have made more particular reference to cellulose acetate as the pellicle base toivbe used. for the various layers, it is to be understood that I do not restrict my invention to the use of cellulose acetate, as various other materials, particularly, other carbohydrate esters, may be used for the pellicle containing the hygroscopic substance alone or with an electrolyte.

While, in describing my invention, I have referred to it as embodied in a body Without a backing and as embodied in a backing it is to be understood 4that by neither of these terms do I exclude films wherein the pellicle which more particularly exemplifies theinvention may have applied to its (normally) exposed surface a coating of such character as not to destroy the efficacy ofthe pellicle, the pellicle, from the standpoint'of the present invention, yet `being Without a backing-7 or being a backing as the case may be.

Of course, should it be desired for any reason, both the film base and the backing of a backed film may contain the conductivity-increasing substances.

I claim:

1. A transparent fiexible, thin, substan-` tially neutral photographic film having a body of carbohydrate ester containing glycerine.

2. A substantially neutral, flexible photographic film containing a hygroscopic sub- `stai1ce and an electrolyte.

a backing, .said backing comprising t to 16 c5 parts of' a pellicle base and 0.25 to 15 parts of 'glycerine l 7. A photographic filmhaving a base and a backing, said backing 'comprising 6 parts of a pellicle base and l part of glycerine.

8. A photographic film having a base and a backing, said backing comprisin'gl to 16 parts of a pellicle base, a hygroscopic substance, and 0.25 to l0 parts of ammonium acetate.

0. A photographic film having a. base and a backing, said backing comprising 0 parts 16 parts of a pellicle base, 0.25' to 15 parts 90,

of glycerine, and 0.25 to- 10 parts of ammonium acetate.

' 13. A photographic film having a base and a backing, said backing comprising 6 parts of a pellicle base, 1 part of glycerine, and 1 part of ammonium acetate.

14. A photographic film having a base and a backing, said backing being of cellulose actate and more conductive than said base. 1

15. A photographic film having a backing of cellulose acetate containing not over 55% combined acetic acid.

16. A photographic film having a base and a backing each of cellulose acetate, the cellulose acetate of said backingbeing of greater conductivity than is the cellulose acetate of said base.-

17. A photographic film having a base and a backing each of cellulose acetate, the cellulose acetate'of said backing being of greater hygroscopicity than/is the cellulose acetate of said base.

18. A photographic film having a base and a backing each of cellulose acetate, the cellulose acetate of said backing having aflovv'er combined acetic acid content than the cellulose acetate-of said base. -v

19. A photogra hic film having a base, and a backing eac of cellulose acetate, .the cellulose acetate of said base having more than 55% combined acetic acid, vand the cellulose acetate oisaid .backing having a lower percentage ofl combined acetic acid than has saidebase.`

20. A photographic film having a base and a backing each of cellulose. acetate, the cellulose acetate of said base having-'more than 55% combined acetic acid, and the cellulose acetate oflsaid backing having not over 55% combined acetic acid.

21. A flexible, thin, substantia1ly neutral photographic lilm including a laye-r of cellulose acetate containing a conductivity-increasing substance.

22. A photographic film having a backing of cellulose acetate lia-.ving not over 55% combined acetic acid and containing a conductivity-increasing substance.

23. A photographic film having a base and a backing each of cellulose acetate, the cellulose acetate of said base having more than 55% combined acetic acid, and the cellulose acetate of said backing having not over 55%y combined acetic acid, said backing containing a conductivity-increasing substance.

24. A photographic film having a base and abackingeach oflcellulose acetate, the cellulose acetate of said base having more than 55% combine-d acetic acid, and the cellulose acetate of said backing having not over 55% combined acetic acid, said'backing-containing. 4 to 16 parts of cellulose acetate, and 0.2.5 to 15 parts of glycerine.

25. A photographic film having a base and a backing each of cellulose acetate, the

cellulose acetate of said base having more than 55% combined acetic acid, and the cellulose acetate of said backing having not over 55% combined acetic acid, said backmg containing 6 parts of cellulose acetate,

e and 1 part of gly'cerine.

26. A photographic lilm having a base and a backing each of cellulose acetate, the cellulose acetate of said base having more than 55% combined acetic acid, and the cellulose acetate of said backing having not ovell 55% 4combined acetic acid, said backing containing 4 to 16 parts of cellulose acetate, a hygroscopic substance, and 0.25 toV 10 parts of ammonium acetate. v

27. A photographic lm having a base and a backing each of cellulose acetate, the cellulose acetate of said base havinggmore than 55% combined acetic acid, and the cellulose acetate of said backing having not over 55% combined acetic acid, said backing containing 6 parts of cellulose acetate,

a hygroscopic substance, and 1 part of ammonium acetate.

28. A photographic iilm having a base and a backing each .of cellulose acetate, the cellulose acetate of said base having more than 55% combined acetic acid, and the cellulose acetate )f said backing having not ovei` 55% combined acetic acid, said backing containing -l to 16 parts ol" cellulose acetate, 0.25 to 15 paitsof glycerine, and an electrolyte.

29. A photographic film having aibase and a backing each of cellulose acetate, the c-ellulose acetate of said base having more than 55% combined acetic acid, and the cellulose acetate of said backing having not over 55% combined acetic acid, said backing containing 6 parts of cellulose acetate, 1 part ot glycei'ine, and an electrolyte.

30. A photographic lilm having a base and a backing each of cellulose acetate, the cellulose acetate of said `base having more than 55% combined acetic acid, and the cellulose acetate of said backing having not over 55% combined acetic acid, said backing containing 4 to 16 parts of cellulose acetate, 0.25 to 15 parts of glycerine, 0.25 to 10 parts of ammonium acetate.

31. A photographic lilm having a base and a backing each of cellulose acetate, the cellulose acetate of said base having more than 55% combined acetic acid, and the cellulose acetate of said backing having not over 55% combined acetic acid, said backing containing 6 partsiotcellulose acetate, 1-v part of glycerine, and 1 part of ammonium acetate. In testimony whereof I aliix my sig/nature. Y

EARLE C. PITMAN. 

